1. Field of the Invention
This invention relates to a composition for a surface modifying agent and in particular, a modified polysiloxane composition capable of forming a film having improved surface properties such as lubricity, non-adhesiveness, etc. on a surface of a rubber article and more specifically, it is concerned with a sanitary rubber article such as a rubber stopper for a medicament, instrument or device for medical treatment, etc. having improved and excellent surface properties by coating the surface with the said composition.
2. Prior Art
Various methods have hitherto been proposed for the purpose of improving the surface property of a molded rubber material, for example, decreasing the surface friction resistance, imparting a solvent resistance, water repellence or ozone resistance, removing the adhesiveness, etc. For example, there have been proposed a process comprising holding a rubber article in chlorine or bromine gas or in a solution of sodium sulfonate (Japanese Patent Publication No. 3807/1982), a process comprising holding a fluorine gas atmosphere (Japanese Patent Publication No. 19464/1983 and Japanese Patent Laid-Open Publication No. 218830/1984), a process comprising coating a rubber surface with an organopolysiloxane composition such as containing an organopolysiloxane having two or more hydroxyl groups bonded to silicon atoms in one molecule, polydiorganosiloxane with both terminal hydroxyl groups blocked, polyorganohydrogensiloxane, epoxy group-containing siloxane and amino- or alkoxy group-containing siloxane, followed by hardening (Japanese Patent Publication No. 47864/1981), a process comprising preparing a medical or sanitary rubber article by incorporating 0.1 to 10% by weight of an organo silicon compound capable of moving little by little in the rubber (Japanese Patent Publication No. 30089/1972), a process comprising coating the surface of a rubber molded article with a silcone raw rubber containing hydroxyl or methoxy groups in the molecule by crosslinking (Japanese Patent Laid-Open Publication No. 96837/1982) and a process comprising producing a rubber stopper by coating and crooslinking a polydimethylsiloxane or a polydimethylsiloxane in which a part of the dimethyl groups is replaced by phenyl groups, vinyl groups, fluorine-containing groups, polyether groups, alkylallyl groups or fatty acid groups (Japanese Patent Laid-Open Publication No. 182418/1982). The inventors have also proposed a process comprising coating a rubber surface with a silane coupling agent containing amino groups as disclosed in Japanese Patent Laid-Open Publication No. 104672/1981) and a sanitary rubber article coated with a modified polysiloxane and a process for the production of the same (Japanese Patent Laid-Open Publication Nos. 318944/1988 and 62170/1989).
In polysiloxane compositions prepared for coating, however, various organic solvents for controlling the viscosity of the compositions and mixing and dissolving various additives are used as a conventional technique, but there is no solvent capable of satisfying all required properties, for example, solubility of the polysiloxane composition, compatibility with the surface of a rubber article, etc.
Since a crosslinking reaction in a polysiloxane composition starts after evaporation of a solvent, there occur delay of the reaction starting time and a large dispersion of the reaction state, depending on the evaporation state of the solvent used, thus causing sliding of the coated film surface of the modified polysiloxane composition, unevenness of the thickness thereof and stripping from the rubber surface.
In a modified polysiloxane-coated saniatry article and a process for the production of the same, the inventors have proposed in Japanese Patent Laid-Open Publication Nos. 318944/1988 and 62170/1989, examples are given in which irradiation of ultraviolet rays was carried out as a means for crosslinking and bonding a modified polysiloxane composition, but it has been desired to further improve the uniformity of the reaction, prevent the polysiloxane film from fine stripping and further shorten the reaction time.